Many portable electronic devices include one or more rechargeable batteries that require external power to recharge from time to time. Such devices may include cell phones, smart phones, tablet computers, laptop computers, wearable devices, navigation devices, sports devices, health devices, medical devices, accessory devices, peripheral input devices, and so on.
Some electronic devices may include an inductive power charging system in lieu of a cable or tethered charging system. In these examples, a user may place the portable electronic device on an inductive power transfer surface (“dock”) to replenish a rechargeable battery via electromagnetic induction. In these systems, an electromagnetic coil within the dock (“transmit coil”) may inductively couple to an electromagnetic coil within the portable electronic device (“receive coil”). By alternating or switching the current through the transmit coil, current may be induced in the receive coil. The portable electronic device may be adapted to use the received current to replenish the charge of a rechargeable battery.
In many cases, portable electronic devices including an inductive power transfer system may require precise positioning and alignment of the portable electronic device and dock. Imperfect positioning or alignment may substantially reduce power transfer efficiency between the transmit coil and the receive coil. In response to imperfect positioning or alignment, many electronic devices increase the power to the transmit coil to ensure the power received by the receive coil is sufficient to be useful to the portable electronic device.
Low power transfer efficiency may result in an increase in the amount of transmitted power dissipated as heat. As a result, the portable electronic device may experience an increase in temperature. In many cases, heating of a portable electronic device may damage or reduce the operative life of the device and/or its components and enclosure. Furthermore, a heated portable electronic device may be unsafe to use in certain circumstances. For example, excess heat from a portable electronic device may present a fire hazard if placed adjacent to flammable material. In other examples, excess heat from a portable electronic device may be uncomfortable, painful, or injuring if that device is suitable to be transported in a pocket or worn in contact with or adjacent to a user's skin, eyes, or clothing. In such examples, a user may be inconvenienced or frustrated by waiting for the device to cool.
Accordingly, there may be a present need for a system and method for efficiently and rapidly delivering useful power to a portable electronic device while effectively managing the temperature thereof.